Influence of Noise in Computer-Vision-Based Measurements on Parameter Identification in Structural Dynamics

Nowadays, consumer electronics offer computer-vision-based (CV) measurements of dynamic displacements with some trade-offs between sampling frequency, resolution and low cost of the device. This study considers a consumer-grade smartphone camera based on complementary metal-oxide semiconductor (CMOS) technology and investigates the influence of its hardware limitations on the estimation of dynamic displacements, modal parameters and stiffness parameters of bolted connections in a laboratory structure. An algorithm that maximizes the zero-normalized cross-correlation function is employed to extract the dynamic displacements. The modal parameters are identified with the stochastic subspace identification method. The stiffness parameters are identified using a model-updating technique based on modal sensitivities. The results are compared with the corresponding data obtained with accelerometers and a laser distance sensor. The CV measurement allows lower-order vibration modes to be identified with a systematic (bias) error that is nearly proportional to the vibration frequency: from 2% for the first mode (9.4 Hz) to 10% for the third mode (71.4 Hz). However, the measurement errors introduced by the smartphone camera have a significantly lower influence on the values of the identified stiffness parameters than the numbers of modes and parameters taken into account. This is due to the bias-variance trade-off. The results show that consumer-grade electronics can be used as a low-cost and easy-to-use measurement tool if lower-order modes are required.

Trajectory Identification for Moving Loads by Multicriterial Optimization

Moving load is a fundamental loading pattern for many civil engineering structures and machines. This paper proposes and experimentally verifies an approach for indirect identification of 2D trajectories of moving loads. In line with the "structure as a sensor" paradigm, the identification is performed indirectly, based on the measured mechanical response of the structure. However, trivial solutions that directly fit the mechanical response tend to be erratic due to measurement and modeling errors. To achieve physically meaningful results, these solutions need to be numerically regularized with respect to expected geometric characteristics of trajectories. This paper proposes a respective multicriterial optimization framework based on two groups of criteria of a very different nature: mechanical (to fit the measured response of the structure) and geometric (to account for the geometric regularity of typical trajectories). The state-of-the-art multiobjective genetic algorithm NSGA-II is used to find the Pareto front. The proposed approach is verified experimentally using a lab setup consisting of a plate instrumented with strain gauges and a line-follower robot. Three trajectories are tested, and in each case the determined Pareto front is found to properly balance between the mechanical response fit and the geometric regularity of the trajectory.

Resistant hypertension: Renal denervation or pharmacovigilance? Insights from a renal denervation screening program

BACKGROUND

With emerging new therapeutic concepts including renal denervation (RDN), there is a renewed interest in resistant hypertension (ResH). Among patients suspected of having ResH, a definitive diagnosis needs to be established.

OBJECTIVES

This study presents observations from a standardized single-center screening program for RDN candidates, including medical therapy modification and reassessment.

MATERIAL AND METHODS

All patients referred to our center for RDN underwent a standardized screening protocol. Candidates were recruited from among patients receiving no less than 3 antihypertensive drugs, including diuretics with office blood pressure (BP) >140/90 mm Hg. The assessment included 2 measurements of BP and ambulatory BP monitoring (ABPM). If needed, pharmacotherapy was intensified and the diagnosis of ResH was reconfirmed after 6 weeks. If ResH was persistent, patients were hospitalized with repeated ABPM on day 4. Further, renal CT-angio was performed and a multidisciplinary team discussed the patients' suitability for RDN.

RESULTS

A total of 87 patients with a ResH diagnosis were referred for RDN. Mean office BP was 159/92 (±7.0/6.5) mm Hg and mean ABPM was 154/90 (±9.0/4.8) mm Hg. The initial medication included angiotensin convertase inhibitors (ACE-I, 78%), angiotensin receptor blockers (12%), β-blockers (85%), calcium channel blockers (36%), and diuretics (93%). During the 18 months of the RDN program, 5 patients underwent RDN and 2 further had ineligible renal anatomy. A new diagnosis of secondary hypertension was made in 21 patients. However, in 59 patients, BP control was achieved after optimization of medical therapy, with a mean ABPM of 124/74 mm Hg. The final treatment included ACE-I (100%), β-blockers (92%), indapamide (94%), amlodipine (72%), and spironolactone (61%). Medication in most of these patients (88%) included single-pill triple combination (52.5%) or double combination (35.6%).

CONCLUSIONS

Patients with elevated BP screened for RDN require a rigorous diagnostic workup. Up to 2/3 of patients can be managed with strict pharmacotherapy compliance and pharmaceutical intensification, including single-pill combinations and improved drug compliance. Hasty use of RDN may be a result of poor drug optimization and/or compliance. It does remain a viable treatment option in thoroughly vetted ResH patients.

Optimal Placement of Virtual Masses for Structural Damage Identification

Adding virtual masses to a structure is an efficient way to generate a large number of natural frequencies for damage identification. The influence of a virtual mass can be expressed by Virtual Distortion Method (VDM) using the response measured by a sensor at the involved point. The proper placement of the virtual masses can improve the accuracy of damage identification, therefore the problem of their optimal placement is studied in this paper. Firstly, the damage sensitivity matrix of the structure with added virtual masses is built. The Volumetric Maximum Criterion of the sensitivity matrix is established to ensure the mutual independence of measurement points for the optimization of mass placement. Secondly, a method of sensitivity analysis and error analysis is proposed to determine the values of the virtual masses, and then an improved version of the Particle Swarm Optimization (PSO) algorithm is proposed for placement optimization of the virtual masses. Finally, the optimized placement is used to identify the damage of structures. The effectiveness of the proposed method is verified by a numerical simulation of a simply supported beam structure and a truss structure.

The impact of various protective tools on the dose reduction in the eye lens in an interventional cardiology-clinical study

The aim of the study was to check, in clinical practice, the potential for the dose reduction of lead eyewear and a ceiling-suspended shield used to protect the eye lens of physicians working in interventional cardiology. To this end, for the lead eyewear, the dose reduction factors were derived to correct the readings from a dosimeter used routinely outside the glasses. Four types of lead eyewear with attached loose thermoluminescent dosimeters and EYE-D dosimeters were worn by physicians in two clinical centres, for two-month periods, during coronary angiography (CA), percutaneous coronary intervention (PCI), and pacemaker procedures. In order to analyse, separately, how a ceiling-suspended lead screen absorbs the scattered radiation, a series of measurements was carried out during single CA/PCI procedures performed with and without the protection. The lead eyewear may reduce the doses to the eye closest to the x-ray tube by a factor between 1.1 and 3.4, depending on its model and the physician's position. The effectiveness of the eyewear may, however, vary-even for the same model and physician-almost twofold between different working periods. The ceiling-suspended shield decreases the doses in clinical practice by a factor of 2.3. The annual eye lens doses without the eyewear estimated from routine measurements are high-above or close to the new eye lens dose limit established by the recent EU Basic Safety Standards, even though the ceiling-suspended shield was used. Therefore, to comply with the new dose limit that is set in the Directive, protection of the eyes of physicians with high workloads might require the use of both the eyewear and the ceiling-suspended shield.

Molecular analysis of the nucleoprotein gene of canine distemper virus isolated from clinical cases of the disease in foxes, minks and dogs

In this study, we used RT-PCR to detect and characterize canine distemper virus isolated from 9 naturally infected foxes, 3 minks and 3 dogs in Poland by amplifying and sequencing a portion of the NP gene. A 293-bp fragment of the CDV NP gene was amplified by RT-PCR. Sequencing of the PCR products from the isolates led to the identification of 3 sequence variants. The mostly representative polymorphic variant No. 1 showed high homology with Chinese isolate of CDV with a accession number EF 375619. The sequences of all isolates from this polymorphic variants compared with the sequences of other polymorphic variants obtained in the study and with European and American isolates sequences from GenBank showed the conservative nucleotides changes in positions 57, 132, 143, 159 and 237. These mutations can indicate that in this part of Europe there are new variants of CDV.